At first glance, Azurill may seem like another forgettable baby Pokémon. This poor water mouse is easily overshadowed by its evolved forms – Marill for igniting the myth that became Pikablu, and Azumarill for its use in competitive play. Indeed, the only memorable characteristic about this Pokémon is its frowning sprite, probably begging to be put out of its misery for being relegated to Gen II dex filler. However, do not let that incredibly heart-wrenching face fool you, because Azuril does have one thing that sets it apart from the other 721 Pokémon currently in existence. Azurill, upon evolution, can change its gender. Azurill is a hermaphrodite.
Until Generation VI when this was fixed, Azurill had a gender ratio of 75% female and 25% male, while both Marill and Azumarill had an even 50:50 split between male and male. Thus, upon evolution into Marill, female Azurills actually had a one in three chance of swapping gender and evolving into a male Marill. Imagine the surprise of the unsuspecting player to find out the female Azurill they had raised and probably given a gender-appropriate name was now a male.
In biology, this phenomenon is referred to as hermaphroditism, and an organism that has both the reproductive organs of both the male and female sexes is a hermaphrodite. This trait is most common in invertebrates such as gastropods, earthworms, and jellyfish, as well as flowering plants.
Hermaphrodites fall into two categories – simultaneous and sequential. Simultaneous hermaphrodites continuously bear male and female reproductive organs throughout their lives. Garden snails are a well-known example of simultaneous hermaphroditism. The snails still mate and produce offspring that are genetically unique, however self-fertilization is not uncommon for simultaneous hermaphrodites, as plants often self-fertilize in the absence of pollinators. Some organisms such as earthworms have defenses in place to prevent self-pollination.
The world of simultaneous hermaphroditism is a fascinating if not strange place, as evident by the unsettling number of photos of invertebrates in various stages of copulation I’ve been forced to shuffle through in order to write this blog post. But personally, I find the sequential hermaphrodites more interesting, in that they are born as one sex but later switch later in life.
A creature such as Azurill, would be classified as a protogynous hermaphrodite, an organism that was born female but changes to a male. Protogyny is common among fish, some of the few vertebrates that exhibit hermaphroditism. Female wrasses, for example, may change into males upon a shortage of the opposite sex, developing testes in place of ovaries. However, this change is irreversible, and only females can make the change, although, under laboratory conditions, males have been known to also swap genders.
Azuril appears to fall into the same boat of the wrasse, with females being the only ones able to change gender, as well as it being an irreversible process. While the in-game cause of this phenomenon may lie in perhaps an oversight on the game designer’s part, from a pure evolutionary viewpoint, Azuril’s hermaphroditism could provide a similar benefit as the wrasse, balancing out the gender ratios when they fall out of whack. But that’s just me applying real world logic to a videogame, again.